Last year’s wildfire season set a record with more than 10 million acres burned. That’s more land than Maryland, the District and Delaware combined. More than half the total was the result of mega-fires in Alaska, where dryness due to historically low mountain snowpack and a freak lightning storm created perfect conditions for a huge blaze.

Humans are altering the planet, including long-term global geologic processes, at an increasing rate. Any formal recognition of an Anthropocene epoch in the geological time scale hinges on whether humans have changed the Earth system sufficiently to produce a stratigraphic signature in sediments and ice that is distinct from that of the Holocene epoch.